Bonjour toute le mondes, j’aimerais ditesre que c’est mona premièrer fois dans cettsur ce site iInternet, je suis très content d’être là avec vous.

"tout le monde" literally means "all the world" (world = people, here) so it's "world" in the singular and "tout" as it's a masculine word
"fois" is feminine => première
In French just like in English, you're "sur" ("on") a website (and "site" is masculine => ce)
"Internet" is considered a proper name, so it's capitalized